[x86] Disable AVX unless the operating system explicitly claims to support it.

test/unittests/base/cpu-unittest.cc

Index: test/unittests/base/cpu-unittest.cc
diff --git a/test/unittests/base/cpu-unittest.cc b/test/unittests/base/cpu-unittest.cc
index 5c58f862381f8e585ddaafd4b5b7627977990cbd..c12e339701c865a4fe7e4abcbc6a5fbe9570321f 100644
--- a/test/unittests/base/cpu-unittest.cc
+++ b/test/unittests/base/cpu-unittest.cc
@@ -18,6 +18,8 @@ TEST(CPUTest, FeatureImplications) {
   EXPECT_TRUE(!cpu.has_ssse3() || cpu.has_sse3());
   EXPECT_TRUE(!cpu.has_sse41() || cpu.has_sse3());
   EXPECT_TRUE(!cpu.has_sse42() || cpu.has_sse41());
+  EXPECT_TRUE(!cpu.has_avx() || cpu.has_sse2());
+  EXPECT_TRUE(!cpu.has_fma3() || cpu.has_avx());
 
   // arm features
   EXPECT_TRUE(!cpu.has_vfp3_d32() || cpu.has_vfp3());